Untitled Notebook.pdf - Cell Cycle

Section 2: Nucleosome Refers to a complex of DNA and histone proteins to promote/guide coiling of DNA Composed of 200 DNA nucleotides coiled around a core of 8 histone proteins histone proteins are positively charged P04- groups on DNA are negatively charged Domainchromosome Crometers Chromati...

Section 2: Nucleosome Refers to a complex of DNA and histone proteins to promote/guide coiling of DNA Composed of 200 DNA nucleotides coiled around a core of 8 histone proteins histone proteins are positively charged P04- groups on DNA are negatively charged Domainchromosome Crometers Chromatin in non-dividing nucleus or interphase: Has nuclear zones wrapped into higher order coils called solenoids Leads to fiber, 30 nm in diameter = 30 nm fiber Chromatin during mitosis Arranges solenoids around scaffold of protein for maximum compaction Radical looping to scaffold protein aided by condensin proteins chromatin compaction during mitosis = inactive Chromatin during interphase = active ma Karyotype: array of chromosomes of an individual organism Arranges, chromosomes by size, staining properties, location of centromere humans are diploid (2n) Haploid (n) : refers to one set of chromosomes = 23 in humans Homologous chromosomes: Pair of same kind of chromosome Each one is homologous entrome · & non-replicatea some Section 3 ] Interphase MitosisThesis] M phase - Gl-Clongest phase) major growth of cell S replication of DNA - G2-organelles replicate microtubules organize (final touches before mitosis) , M(mitosis) : separation of nucleus , subdivided into 5 phases C (cytokinesis) : separation of cytoplasm forI new cells Mammalian cell takes 24 hours · Centromere - point of constriction Kinetochore-attachment site for microtusa each sister chromatid has a centromere chromatids stay attached at cohesin centromere by  section 5 Mitosis is divided into 5 phases 1) Prophase 2) Prometaphase 3) Metaphase 4) Anaphase 5) Telophase Phophase : chromosomes are condensing into 38 spindles begin to , form , nuclear envelope breaks down Prometaphase : after nuclear envelope disassembly microtubles , attachment to chromosome Kinetochrove chromosomes start moving to center of cell-congression assembly and of microtubles - disassembly Motor proteins Kinetochore - at Metaphase - alignment of chromosomes along metaphase plate , axis of cell division Anaphase - removal of cohesin proteins , centromeres split , sister chromatids pulled to opposite poles - Anaphase A - Kinetochores pulled toward poles Anaphase B spindle poles - - move apart Telophase spindle disassembles , new cytoskeleton nuclear envelope forms around each set of sister - , chromatids (now called chromosomes) , chromosomes begin to uncoil , nucleolus reappears , mitosis completed Cytokinesis-clearage of the cell into equal halves Animal cells - constriction of acting filaments produces a clearage furrow Plant cells - cell plate forms between the nuclei  Checkpoint cell cycle has two irreversible points / - replication of genetic material -separation of the sister chromatics cell cycle can be put on hold at specific points called checkpoints 3 checkpoints 1) Gi/s checkpoint-cell "decides" to divide. Cell commits to DNA replication (Sphase) · Grow factors are peptides that signal for cells to grow/divide · halts isdna damage , starvation conditions , lack of growth factors 2) G2/m Checkpoint - cell makes a commitment to mitosis , assesses success of DNA replication · halts dna if damage · Genomic Fidelity : lack of accuracy in replication in DNA 3) Spindle checkpoint - cell ensures that all chromosome are attached to spindle commits to separation of chromosomes during anaphase halts if not all kinetochores are attached to spindle - - - are all chromosomes attached x to spindle IS DNA replicated accurately ↓ are growth factors present ? is the environment favorable ?  Cdks (Cyclin-dependent Kinases · primary mechanism of cell cycle control · Cdks partner with different cyclins at different points in the cell cycle Cdk-cyclin complex also called mitosis promoting factor (MPE activity of Cak is controlled by pattern of phosphorylation · Phosphorylation at one site inactivates cak while phosphorylation at another site actives CdK · Multiply Cdks control the cell cycle Mammalian cell MFPs (cdk-cyclin) Gi/s-Cdk2/cyclin E G2/M-Cdk1/cyclin B Spindle checkpoint - APC APC - anaphase promoting complex spindle checkpoint - presence of all chromosomes at the Metaphase plate and the tension on the microtubles between opposite poles are both important The function of APC/C is to trigger anaphase itself Cellular Proliferation : process by which cells grow and divide to create new cells , which increases # of cells Growth factors + Specify cell surface receptor= start to signals , reactions to Cdk proteins to start cell divison Without control of cell two types of genes can disturb the cell cycle when they are mutated cycle : uncontrolled of cells 1 Tumor-suppressor genes growth ·. · failure of cell cycle control 2. Proto-oncogenes p53-plays a key role in G , checkpoint p53 protein monitors the integrity of DNA , if DNA is damaged , cell division is halted and repair enzymes stimulated if DNA damage is irreparable , p53 directs cell to kill itself p53 is absent or damaged in many cancerous cells. tumor-suppressor gene ex : (Rb) retinoblastoma susceptibility - predisposes individuals for rare form of cancer that affects the retina of the eye  Proto-oncogenes · normal cellular genes that become oncogenes when mutated (oncogenes can cause cancer ( - Sexual life cycle Somatic cells : are diploid · made up of meiosis and fertilization -undergo mitosis to form two genetically identical Diploid Cells daughter cells · Somatic cells of adults have 2 sets of chromosomes Haploid cells : Germ-line cells : are diploid · Gametes have only I set of chromosomes -undergo meiosis to produce haploids gametes after puberty is offspring inherit genetic material from 2 parents Haploid sperm -Fertilization Diploid Zygote Meiosis : two rounds of division - meiosis 1 and meiosis 11 (each has prophase , metaphase , anaphase, telophase Before meiosis : Synapsis-homologous chromosomes become closely associated "Chiasmata" ma Genetic recombination between nonsister chromatids Chiasmata-site of crossing over - Genetic recombination 1st meiosis division is termed the "reduction division" meiosis 1 divisions · called reduction division= formation of haploid cells Meiosis 11 division · DNA replication between meiotic division · does not reduce chromosome number · separates sister chromatids for each homologue  meiosis meiosis 2 prophase I prophase 2 metaphase metaphase 2 anaphase anaphase 2 telophase telophase 2 Prophase 1 : chromosomes coil tightly , nuclear envelope disappears , spindle forms · each chromosome composed of 2 sister chromatics Synapsis-homologues become closely associated · , cross over occurs between non-sister chromatics remain attached at chiasmata · metaphaseI : · terminal chiasmata holding homologues · microtubules from opposite pole attach to each homologue (not each sister chromatics) Homologues aligned · are at metaphase plate Anaphase 1 : · microtubules of the spindle shorten homologies · are separated from each other and more to opposite poles Telophase 1 : · nuclear envelope reforms around each daughter nucleus · cytokinesis may or may not occur after telophase & Prophase 11 : nuclear envelope dissolves and new spindle apparatus forms metaphase 11 : chromosome align on metaphase plate Anaphase 11 : Sister chromatids are separated from each other Telophase 11 : nuclear envelope reforms around 4 set of daughter chromosomes ; cytokinesis follows Final result : 4 cells containing haploid sets of chromosomes · Meiosis 11 errors nondisjunction - failure of chromosomes to move to opposite poles during either meiotic division Aneuploid gametes - gametes with missing or extra chromosomes Unique aspects of Meiosis · synapsis and crossing over · sister chromatids remain joined at their centromere throughout meiosis · kinetochores of sister chromatids attach to the same pole in meiosis/ · DNA replication is suppressed between meiosis 1 and meiosis 11 Human Female reproductive system : · at puberty , granulosa cells secrete estrogen · at birth ovaries contain about 1 million follicles · human menstrual cycle last-1 month Human Male reproductive system · seminiferous tubules - sites of sperm production · leydig cells produce testosterone 15 million new sta cases in USA each year more than 25 diseases are spread primarily through sexual activity  Chapter 12 Josef Kolreuter - 1760 - crossed tobacco strains to produce hybrids that differed from both parents T A.. Knight-1823- crossed 2 varieties of garden pea , Pisum sativa pea plants study : Gregor Mendel 1) Other research showed that pea hybrids could be produced 2) Many pea varieties were available 3) Peas are small plants and easy to grow 4) peas can self-fertilize or be cross-fertilized Mendel's experimental method (3 stages 1) produces true-breeding strains for each trait he was studying 2) Cross-fertilize true-breeding strains alternate forms of trait having a - Also perform reciprocal crosses 3) Allow the hybrid offspring to self-fertilize for several generation and count the number of offspring showing each form of the trait Monohybrid Crosses Are crosses to study only two variations of a single trait Used by Mendel to produce true breeding pea, stains for seven different traits Each of 7 traits had only two variants